Is joule thief circuit gets overunity?

[poynt99]

One other important issue to be keenly aware of Lawrence, is that your CH1 (A1-A2) probe is NOT giving you an accurate measurement of the true battery voltage for making the input power computation. You are in fact measuring across both the battery and the battery CSR resistor.

In order to obtain the true battery voltage measurement from the A1-A2 difference, you must subtract the voltage drop across the battery CSR (A4-A3) from the A1-A2 measurement.

Since A1-A2 is positive, and A4-A3 is negative, subtracting the two is equivalent to adding the two. So in fact your battery voltage is actually higher than what your A1-A2 probe is capturing, and as such, your input power result will be higher (in the negative direction) as well.

Of course you would need to do this computation in the spread sheet.

[ltseung888]

One other important issue to be keenly aware of Lawrence, is that your CH1 (A1-A2) probe is NOT giving you an accurate measurement of the true battery voltage for making the input power computation. You are in fact measuring across both the battery and the battery CSR resistor.

In order to obtain the true battery voltage measurement from the A1-A2 difference, you must subtract the voltage drop across the battery CSR (A4-A3) from the A1-A2 measurement.

Since A1-A2 is positive, and A4-A3 is negative, subtracting the two is equivalent to adding the two. So in fact your battery voltage is actually higher than what your A1-A2 probe is capturing, and as such, your input power result will be higher (in the negative direction) as well.

Of course you would need to do this computation in the spread sheet.

@poynt99:

Thank you for the reminder.  All my spreadsheets have the above mentioned computation.  You have Board 33 and can easily do the actual experiments.  I am showing the details of Board 80 for those who want to replicate and improve.  Please show the results of Board 33 on your 4 channel Scope.  There will be more to discussions as far as the theory is concerned.  For now, we just need to ensure that there are NO experimental or equipment errors.

[TinselKoala]

TK,

Actually, according to the latest scope shot and the circuit diagram of the probe locations, the power polarities seem correct.

The output power will be a positive result, and the input power a negative result. This is exactly what one would expect from a circuit where the battery is supplying a net power, IF the scope probes are NOT reversed polarity with reference to the battery and battery CSR.

In such a case, the supply always results in a negative power, and any load results in a positive power. I've gone over this issue several times in the past.

The voltage drop across the battery CSR will be inverted wrt the polarity of the voltage drop across the battery, and in Lawrence's case, since the scope probes across these two points are NOT reversed, this will result in a negative power product, as it should.

However, this does NOT indicate the battery is being charged, quite the contrary; it clearly indicates that it is supplying a net power to the circuit, and it is depleting normally.

I think you are missing my main "poynt". If you look carefully at the circuit diagram, and look carefully at the photo that goes with it, you will see that the probe in the example photo is reversed from the hookup given in the circuit diagram. The photo shows the probe _TIP_ connected to the common circuit ground.  How is it possible to make simultaneous input voltage and current measurements if the probe is hooked up as the _photo_ shows?

[TinselKoala]

Replicate and improve? How about this. You've seen this before but you obviously didn't get the message. Ease of manufacture, elimination of circuit errors, consistency between individual units, cost reduction, complexity reduction.....

Of course, since my test points are directly at the respective current monitoring resistors and my current paths are in general shorter and more direct than yours... I am likely to see less artefactual waveform distortions than you are.

Proudly displaying my construction "improvements" in my "replication" of a circuit that I actually built well before you started using it:

(It's hard for me to believe that after all this time, someone hasn't spent ten minutes with a circuit CAD program and generated a nice template for Lawrence, that he could send off and get made into boards professionally for minimal cost. I put this together completely manually in an afternoon as a sort of a joke.)

[TinselKoala]

TK,

Actually, according to the latest scope shot and the circuit diagram of the probe locations, the power polarities seem correct.

The output power will be a positive result, and the input power a negative result. This is exactly what one would expect from a circuit where the battery is supplying a net power, IF the scope probes are NOT reversed polarity with reference to the battery and battery CSR.

In such a case, the supply always results in a negative power, and any load results in a positive power. I've gone over this issue several times in the past.

The voltage drop across the battery CSR will be inverted wrt the polarity of the voltage drop across the battery, and in Lawrence's case, since the scope probes across these two points are NOT reversed, this will result in a negative power product, as it should.

However, this does NOT indicate the battery is being charged, quite the contrary; it clearly indicates that it is supplying a net power to the circuit, and it is depleting normally.

Perhaps the following attached pix will help clear up the issue.
In the first simple diagram below I have shown a battery, a voltmeter (separate and isolated), a current-viewing resistor , the connecting wire and two test points A and B. A would usually be considered the "common circuit ground".... except when also monitoring output in Lawrence's circuit too, "B" must be used as the common reference point for all 4 scope probes.
"Conventional" electric current flows from positive to negative and this would indicate normal battery discharging as it dissipates energy in the circuit. The isolated voltmeter reads the battery voltage and at the correct polarity. Now hook a scope to points A and B. Clearly, point B will be at a higher positive voltage than point A when current is flowing conventionally. So if you hook your scope TIP to point B and your reference "ground" lead to point A, you will see a _positive_ voltage indicated on the scope when current is flowing conventionally and the battery is discharging. This positive voltage is the "drop" across the resistor and gives the current thru the resistor by Ohm's law.
But the circuit Lawrence uses requires that the common ground actually be at point B. So the current must be monitored with probe TIP at point A-- where the voltage is _lower_ than at the probe's reference lead at point "B". This means the scope will indicate a NEGATIVE voltage when current is flowing conventionally and the battery is discharging. This negative voltage _reading_ when multiplied by the voltmeter's positive reading will yield a "negative" power value. To avoid confusion, many people (like me) would simply press the trace invert button to make the reading agree with the _conventional_ definition of current flow.
Now, look at the schematic of Lawrence's circuit. He correctly has the common circuit ground at the point corresponding to my point "B", and the input current probe TIP at the battery negative, my point "A". This means that, _{without using the trace invert function}, the computed power _should_ be "negative" when the current is flowing normally, just as Poynt99 has explained many times.
However.... the PHOTOGRAPH that Lawrence has recently provided shows the probe TIP at the common circuit ground ( my point "B")  and the probe ground at the battery negative (my point "A"). This will invert the current reading, and also create a ground path through any other instrument grounds that might be connected to the correct common circuit ground.
So I have asked about this. What's the explanation for the discrepancy between the PHOTO showing how Lawrence has recently been measuring, apparently incorrectly, and the SCHEMATIC which shows what I would consider to be correct probe hookups, but which will give an _apparent_ negative power unless the channel trace invert function is used?